Decreased Smell and Taste: Common Bedfellows

"Doc, I can’t smell and taste certain things anymore. Do you think it’s from my allergies?"

Allergists and otolaryngologists (Ear, Nose and Throat doctors) frequently see patients with complaints of decreased sense of smell, often associated with some loss of taste. In fact, eighty percent of people who have sensory problems with smell also have a problem with taste sensation. Smell and taste disorders can be particularly disturbing around holidays when so many festive events are accompanied by extravagant meals.

First let’s get familiar with the terminolognosmia is the term used for complete loss of the ability to smell but most people experience partial loss.** Hyposmia** means decreased ability to smell (much more common).** Ageusia** is the term used for complete loss of taste.** Hypogeusia** means decreased ability to taste (also the more common of the two).

Doctors will usually respond with these questions:
- When did it begin?
- Do you have a complete or partial loss of smell or taste? - Has it been continuous or intermittent (do you have full sensation at times?)
- Is it progressing in severity?
- Do you have previously identified allergy triggers and a diagnosis of allergic rhinitis?
- Do you have chronic or recurring nasal blockage?
- Have you ever had nasal polyps?
- Have you ever had sinus surgery or brain surgery?
- Have you previously had head trauma?
- What medications have you been taking?

About Sense of smell The sensation of fumes, odors, fragrances, aromas, gases and other chemicals comes from receptors located on nerve endings located deep in the upper recesses of the nose. The** olfactory nerve** is the cranial nerve responsible for the sensation of smell. It may fail to send appropriate signals to the brain if it is damaged by physical trauma (moving vehicle accident, punch to the face or nose, sinus or brain surgery etc.).

Chemical trauma may also damage nerve endings that convey important signals to the brain. These include toxic fumes and combusted materials (smoke) as well as nasal sprays (some zinc salts).

The olfactory nerve won’t get a chance to pick up a smell signal if pathways leading to it are blocked. Nasal congestion from allergic or non-allergic rhinitis, common cold, flu, sinusitis or other forms of rhinitis may cause decreased sense of smell. Nasal passages comminly become blocked by nasal polyps which diminish the ability to smell. A severely deviated septum may also cause decreased smell. Rarely, tumors (in tobacco smokers) or foreign objects (especially in young children) may cause of enough blockage to affect smell sensation.

Seven things you can do if you are concerned about your sense of smell:

Discuss your concerns with your primary care physician. Be prepared by listing the ten questions I referred to above, with your answers. Have your answers ready for the specialist if you are referred to one.

If you are using any nasal sprays containing zinc, stop them immediately.

If you work in a factory or around any chemicals or fumes, see if you can get a material safety data sheet (MSDS) from your supervisor or employer.

They are legally obligated to provide it for you if it exists.

Ask if any co-workers are experiencing similar sensory symptoms.

Be sure to alert your doctor if you have hypersensitivity (allergic to) aspirin. Aspirin allergy, nasal polyps and asthma represent a disease state referred to as Samter’s Triad.

If you have been on a special diet for several weeks or months (not under physician guidance) discuss it with your healthcare provider. Malnutrition and some vitamin deficiencies may cause decreased smell. Ironically, zinc is one of them.

A more comprehensive workup should be considered for those over age 60. The list of possible causes is longer and permanent
loss of smell more common. Referral to a specialist (ENT or Neurologist) should be considered in this setting.

In Summary

Some hyposmia is common in the setting of allergic rhinitis but it is usually not the main complaint. When I see patients are most disturbed about loss of smell (over other nasal and sinus complaints), I am more concerned about other problems complicating allergic rhinitis. A thorough history and physical exam will help me determine how to initially treat the problem and whether ordering tests or referring to ENT or Neurology is indicated. Hyposmia and hypogeusia associated with upper respiratory infections should be short-lived, so if these symptoms have lasted more than a few weeks they deserve further attention.